关于EF延时加载的面试题

   public async Task<ActionResult> GetData()
   {
       var data = (from leftdata in GetLeft()
                   join rightdata in GetRight() on leftdata.Id equals rightdata.Id into tempdata
                   from matchdata in tempdata.DefaultIfEmpty()
                   select matchdata).ToList();
       return Ok(data);
   }

   
   private IEnumerable<YourModel> GetLeft()
   {
       return YourDbContext.YourModels.Where(c=>c.Id==1);
   }
   private IEnumerable<YourModel> GetRight()
   {
       return from data in YourDbContext.YourModels
              select data;
   }

上面代码调用GetData()查询了几次数据库？

如果换成IQueryable又如何

 public async Task<ActionResult> GetData()
 {
     var data = (from leftdata in GetLeft()
                 join rightdata in GetRight() on leftdata.Id equals rightdata.Id into tempdata
                 from matchdata in tempdata.DefaultIfEmpty()
                 select matchdata).ToList();
     return Ok(data);
 }

 
 private IQueryable<YourModel> GetLeft()
 {
     return YourDbContext.YourModels.Where(c=>c.Id==1);
 }
 private IQueryable<YourModel> GetRight()
 {
     return from data in YourDbContext.YourModels
            select data;
 }

由于IEnumerable和IQueryable的特性,我原本的想法是使用IEnumerable一共查询了3次数据库，使用IQueryable查询了一次数据库,最后实践发现无论是那种方式都只查询了一次数据库